Pressure transducer assembly having an integral back-up ring

ABSTRACT

A pressure transducer assembly, and a method of making the same, comprising a header having a first connection portion; a port having a corresponding second connection portion, wherein the first connection portion of the header is attached to the second connection portion of the port to create a header-port interface; and an integral back up ring defined in one of the header and port, wherein the integral back up ring is separated from the header-port interface by a cavity. The first connection portion of the header is attached to the second connection portion of the port by a full penetration weld and the integral back up ring is adapted to block the full penetration weld from damaging the header and thus minimize, if not eliminate, crack propagation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part application of copending U.S.patent application Ser. No. 11/978,291, filed Oct. 29, 2007, entitledMETHOD OF JOINING A PRESSURE SENSOR HEADER WITH AN ASSOCIATED TRANSDUCERELEMENT, which is a divisional of U.S. patent application Ser. No.11/036,877, filed Jan. 14, 2005, now U.S. Pat. No. 7,369,032, entitledMETHOD OF JOINING A PRESSURE SENSOR HEADER WITH AN ASSOCIATED TRANSDUCERELEMENT which is a continuation-in-part application of U.S. patentapplication Ser. No. 10/867,029, filed Jun. 14, 2004, now. U.S. Pat. No.7,212,096, entitled PRESSURE SENSOR HEADER HAVING AN INTEGRATEDISOLATION DIAPHRAGM, which is a continuation-in-part of U.S. patentapplication Ser. No. 10/339,725, filed Jan. 9, 2003, entitled PRESSURESENSOR HEADER HAVING AN INTEGRATED ISOLATION DIAPHRAGM, the entiredisclosures of which are hereby incorporated by reference as if beingset forth in their respective entireties herein.

FIELD OF THE INVENTION

The present invention relates to pressure transducers, and moreparticularly to an improved method of joining a pressure sensor headerwith an associated port or other transducer element.

BACKGROUND OF THE INVENTION

Pressure transducers conventionally include pressure sensor headers.U.S. Pat. No. 4,695,817 entitled, ENVIRONMENTALLY PROTECTED PRESSURETRANSDUCERS EMPLOYING TWO ELECTRICALLY INTERCONNECTED TRANSDUCER ARRAYSissued to A. D. Kurtz et al. on Sep. 22, 1987 and assigned to theassignee herein, the entire disclosure of which is hereby incorporatedby reference herein, provides an example. Certain pressure sensorheaders include a metal header shell having a front face with straightor tapered holes and header pins extending therethrough. Well knownfused glass-metal seals sit in the holes and seal the header pins to thefront face of the header shell. Pressure sensor headers commonly operateunder external pressures, for example hydrostatic pressures, which canreach extremes, depending on the sensor application, up to and in excessof 50,000 psi.

Referring now to FIG. 1A, there is shown a graphical representation ofan operation of a pressure sensor header 10 under a hydrostatic pressurethat exposes a front face 12 of a metal header shell 11, as well as thecylindrical side wall 14 of the header shell 11, to pressure forces. Thepressure force N acting on the header shell's cylindrical side wall 14generates compressive tangential and radial stresses (hoop stress) inthe side wall 14. The pressure force F acting on the front face 12 ofthe header 10 pushes on the glass seals 16 and header pins 18. Anexcessive amount of pressure force F on the front face 12 of the header10 can push the pins 18 or glass seals 16 into the header 10, breakingthe glass-metal seals 17 and allowing leakage. The compressive hoopstress generated in the side wall 14 of the header shell 11 compressesor constricts the seals 16 around the pins 18 thereby strengtheningthem. Under even greater hydrostatic pressures, the compressive hoopstress assists in retaining the seals 16 or preventing leaks, than ifthe side wall 14 of the header shell 11 were not exposed to anyhydrostatic pressure.

Referring now also to FIG. 1B, the pressure force N acting on the sidewall of the header shell functions similarly to the frictional forcesbetween the glass seals 16 and the walls 19 of the header pin apertures15. The frictional forces resist the motion, or pushing out, of theglass seals 16 from the pin apertures 15.

The pressure sensor header is ordinarily welded to a port or othertransducer element using a weld area that is typically modeled as athick wall cylinder. To survive these high stresses under pressure, sucha weld area requires the use of a deep, penetrating butt joint weld.Such deep welding processes usually produce localized heat in the headermaterial, which may stress or crack the glass header seals, pins andother header components. Typical design strategies for avoiding suchproblems involve moving the pins and other components away from the zoneaffected by the welding heat. Such designs often involve making theheader larger, or longer in length.

However, these conventional pressure sensor header to port joiningmethods still present various problems. The extreme external pressurestend to fatigue and fracture the welded joints at the header-portinterfaces. Additionally, as described above, the weld heat during thejoining process tends to heat and damage the glass seals. The provisionof larger or longer headers to avoid such weld damage may result in morecostly, heavier or less accurate pressure headers.

Thus, an improved method of joining the pressure sensor header with aport or other transducer element is desired, which provides a higherstrength device that can operate under extreme applied pressures, whilealso avoiding damage to header components during the joining process.

SUMMARY OF THE INVENTION

The various embodiments of the present invention provide a pressuretransducer assembly, and a method of making the same, comprising aheader having a first connection portion; a port having a correspondingsecond connection portion, wherein the first connection portion of theheader is attached to the second connection portion of the port tocreate a header-port interface; and an integral back up ring defined inone of the header and port, wherein the integral back up ring isseparated from the header-port interface by a cavity. The firstconnection portion of the header is attached to the second connectionportion of the port by a full penetration weld and the integral back upring is adapted to block the full penetration weld from damaging theheader and thus minimize, if not eliminate, crack propagation.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the present invention will be facilitated byconsideration of the following detailed description of the preferredembodiments of the present invention taken in conjunction with theaccompanying drawings, wherein like numerals refer to like parts and:

FIGS. 1A and 1B are sectional views through a conventional header underhydrostatic pressure;

FIG. 2 is a sectional view of a pressure transducer assembly utilizingthe invention;

FIG. 3 is a sectional view of a pressure sensor header of the pressuretransducer assembly of FIG. 2;

FIG. 4 is an exploded sectional view of the pressure sensor header andtransducer and port of the pressure transducer assembly of FIG. 2;

FIG. 5 is an enlarged sectional view of the pressure transducer assemblyof FIG. 2;

FIG. 6 is an enlarged view of the area circled in FIG. 5;

FIG. 7 is a schematic end view of a conventional pressure sensor headershowing the application of hoop stress to the header shell;

FIG. 8 is a sectional view of a portion of a conventional pressuretransducer assembly showing how hoop stress causes crack propagation atthe header-port interface;

FIG. 9 is a sectional view of a pressure transducer assembly made withthe tongue and groove joining arrangement of the present invention,showing how the joining arrangement takes advantage of hoop stress tostop crack propagation at the header-port interface;

FIG. 10 is a sectional view of a pressure transducer assembly of theprior art having a weld stop header with a step design;

FIG. 11 provides a close-up view of a back up plate in standard platewelding;

FIGS. 12 a-b provide a sectional view and an enlarged view,respectively, of a butt weld header design;

FIGS. 13 a-c provide various views of an integral back up ring whereinthe ring is defined within the port of the transducer assembly;

FIG. 14 provides an illustration of an integral back up ring, whereinthe ring is defined within the header of the transducer assembly;

FIG. 15 provides a sectional view of a pressure transducer assemblyapplying an integral ring;

FIGS. 16 a-d illustrates transducer assemblies utilizing the integralback up ring of the present invention; and

FIGS. 17 a-b illustrates transducer assemblies utilizing the integralback up ring of the present invention with dimensions for two exemplaryembodiments.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for purposes of clarity, many other elements found in typical pressuretransducer headers and manufacture methods relating thereto. Those ofordinary skill in the art will recognize that other elements aredesirable and/or required in order to implement the present invention.However, because such elements are well known in the art, and becausethey do not facilitate a better understanding of the present invention,a discussion of such elements is not provided herein. The disclosureherein is directed to all such variations and modifications to suchelements and methods known to those skilled in the art.

Referring now to FIG. 2, there is shown an illustrative embodiment of apressure transducer assembly 20 according to an aspect of the presentinvention. The pressure transducer assembly 20 includes a pressuresensor header 22 joined, in accordance with the principles of thepresent invention, with another transducer element or member 24, such asa sensor body or port, at an interface 26 of the header 22 and the othertransducer element 24.

Referring now also to FIG. 3, the pressure sensor header 22 includes abody or shell 30, which is typically made from metal or metal alloy. Theshell 30 has a front end 32, an opposing back end 34, and a side wall 36that may be formed in a stepped configuration with a first cylindricalsurface portion 36 a of a first diameter, and a second cylindricalsurface portion 36 b of a second diameter. A sensor cavity 38 is formedin the front end 32 of the shell 30. The sensor cavity 38 contains asensor element 42, which may be centrally mounted on the floor 40 of thesensor cavity 38. A plurality of cylindrical apertures 44 are defined inthe floor 40 of the sensor cavity 38. The apertures 44 extend throughthe shell 30 to the back end 34 thereof. A number of the apertures 44have a fused, glass seal or bead 48 seated therein, which surrounds apin 46. The pins 46 (only one is visible) are typically constructed of agold-plated, glass sealing alloy, such as Kovar. The fused glass beads48 hermetically seal the pins 46 to the shell 30. The glass-metal seals50 formed by the shell 30 and each pin 46 and fused glass bead 48,prevent pressure medium (not shown) leakage from the front end 32 of theshell 30 to the back end 34 of the shell 30. The fused, glass beads 48also dielectrically insulate the pins 46 from the shell 30. A tube 52 isdisposed in one of the apertures 44. The tube 52 allows the sensorcavity 38 to be filled with a suitable fluid medium, such as siliconeoil, after which the tube 52 may be sealed by welding or otherconventional sealing means.

Referring still to FIG. 3, sensor element 42 electrically communicatesthrough gold bonded wires 54 (only one is visible) with the header pins46. A ceramic insert 56 is disposed in the sensor cavity 38 andsurrounds the pins 46 and the sensor element 42. The ceramic insert 56provides a wire path for the wires 54 and minimizes the required volumeof oil within the sensor cavity 38. An isolation diaphragm 58 is mountedon the front end 32 of the shell 30, over the sensor cavity 38. Theisolation diaphragm 58 forms a header face or front face.

Referring again to FIG. 2, port 24 may be formed as a generallycylindrical, tube-like member defining a conduit 70 that communicateswith an internal port cavity 72 formed at an end 74 opposite theheader-port interface 26. The port cavity 72 mechanically houses,protects, and electrically shields compensation or amplifierelectronics. Signal wires 76 connected to the header pins 46 passthrough the conduit 70 to electrically communicate with either a sensorcable or the electronics 78 located within the cavity 72. A cap-likescreen element 60 is mounted on an outer flange 80 of the port 24,adjacent the header-port interface 26.

The screen element 60 surrounds the header 22, thus, providingmechanical protection for the header 22, while allowing the pressuremedium to pass through it and contact the header 22.

Referring now to FIGS. 4-6 collectively, there are shown a tongue andgroove joining structure or arrangement according to an embodiment ofthe present invention, which is utilized at the header-port interface 26for joining the header 22 to the port 24. In the shown embodiment, thetongue and groove joining arrangement includes a ring-shaped groove orrecessed female element 100 formed in the back end 34 of the shell 30 ofthe header 22. The groove 100 is typically positioned concentricallywith the side wall 36 of the shell 30. A mating or matching ring-shapedtongue or protruding male element 110 is formed on a rim surface 112 ofthe port 24. The tongue 110 is typically positioned concentrically withthe outer side surface 114 of the port 24. It should be understood, thatthe tongue and groove joining arrangement may include a groove (notshown) formed in the rim surface 114 of the port 24 and a correspondingtongue (not shown) formed on the back end 34 of the shell 30 of theheader 22.

The tongue 110 is formed to fit tightly (conventional slip-fit orpress-fit) within the groove 100, upon assembly of the header 22 withthe port 24, to create a weld area 120 at the header-port interface 26suitable for being electron-beam welded, welded using another knownwelding method. The tongue 110 is typically configured to have arectangular-shaped cross-section, such that the tongue 110 protrudesperpendicularly from the rim surface 112 of the port 24 and has threegroove mating surfaces 110 a, 110 b, 110 c, which are substantiallyorthogonal relative to each other. The matching groove 100 would thenalso be configured in a rectangular-shaped cross-section with threetongue mating surfaces 100 a, 100 b, 100 c. The tongue and groove may beconfigured in other cross-sectional shapes, such as semicircular ortriangular.

It is contemplated that he tongue and groove joining arrangement mayalso include two or more grooves or combination of groove(s) andtongue(s) formed in and/or on one of the back end 34 of the header shell30 or rim surface 112 of the port 24 and a matching number of tongues orcombination of tongues and grooves formed in and/or on the other one ofthe back end 34 of the header shell 30 or rim surface 112 of the port24. Furthermore, the tongue and groove joining arrangement may beimplemented with other male-female type joining configurations.

The tongue and groove joining arrangement of the present inventionpermits a full penetration weld 122 (to the tongue 110) to be made inweld area 120 as shown in FIG. 6. This weld extends through theheader-port interface 26 to the mating surfaces 110 c, 100 c of thetongue 110 and groove 100. Hence, the tongue and groove joiningarrangement increases the weld area, as compared with conventional buttwelds or partial welds, thereby increasing the joint strength withoutthe need for increasing the actual wall thickness of the transducerassembly 20.

As mentioned earlier, a pressure transducer assembly may receive veryhigh hydrostatic pressures up to and over 50,000 psi, which act on thefront face and side wall of the header. The pressure acting on the frontface of the header tries to push the glass seals or pins into theheader, which can break the glass-metal seals between the pins and theheader shell, thereby allowing leakage of the pressure medium into theheader, which destroys the header and sensor. The compressive or hoopstress generated by the pressure acting on the side wall of the headerprevents the pins or glass seals from being pushed out of the headerunder the pressure applied to the header face. As shown in FIG. 7, theapplication of hydrostatic pressure to the side wall 14 of header 10produces a hoop stress H that is exerted all around the side wall 36.

The compressive hoop stress H applies constrictive forces on theglass-metal seals, which strengthens the seals and overcomes thepressure acting on the front face, which is trying to push the sealsinto the header 10. In this manner, the extreme external pressures areconverted to an advantageous hoop stress, which aids in preventingleakage resulting from the breakage of the glass-metal seals.

However, such high hoop stresses also tend to cause crack propagation inconventional butt or partially penetrated welds joining the header andthe port together, which may result in weld fracture and fatiguefailure. The tongue and groove arrangement of the inventionsubstantially eliminates such problems by improving on the jointstrength, as well as the strength of the overall pressure transducerassembly.

Unlike conventional joining methods such as butt welds or partialpenetration welds, the tongue and groove arrangement of the inventionaids in preventing crack propagation under static or cyclic loadingconditions. In the case of a conventional partial depth butt weldjoining arrangement, as shown in FIG. 8 and denoted by numeral 130,cracks 134 (only one shown) in the weld 130 frequently occur along theinner circumference 132 of the header-port interface 126. The appliedexternal (hydrostatic) pressure N generates opposing stress forces C,which operate to open the cracks 134. Under cyclic pressure conditions,this repeated force will continue to open the crack, with each cycle.

As shown in FIG. 9, the tongue and groove joining arrangement of thepresent invention turns the direction of the cracks 124 (only one shown)90 degrees so that the leading ends or crack tips 124 a of the cracks124 will be along the outer cylindrical surfaces 110 c, 100 c of thetongue and groove joining arrangement. The hoop stress resulting fromthe external pressure N places the leading ends 124 a of the cracks 124in compression, rather than in tension, therefore the cracks 124 willnot continue to propagate. This application of compression rather thantension stress on the crack has an effect similar to that of drilling ahole at the tip of a crack, to reduce the stress concentration on thecrack tip (the crack tip is where the stress is highest, and is theinitiating point for opening the crack). Thus, the tongue and groovejoining arrangement of the present invention improves on fatiguesurvival rates under cyclic pressure conditions, by preventing crackpropagation in the weld joint area.

Another advantage of the tongue and groove joining arrangement of thepresent invention is that during the welding process, the tongue servesas a stop, thereby preventing the laser or electron beam or otherwelding medium from penetrating further into the joint. As can be seenin FIG. 8, the laser, electron beam or other welding medium maypenetrate through the depth of the conventional partial depth butt weld130, to the internal cavity or other parts of the header, such as theglass seals, pins, signal wires or other internal components, therebydamaging them. However, as can be seen in FIG. 9, the tongue 110 blocksor shields the laser, electron beam or other welding medium and therebypreventing the same from penetrating to the internal cavity or otherparts of the header 22.

The tongue and groove joining arrangement of the present inventiontherefore eliminates the conventional problem of thermal stresses beingapplied to the header sealing glass or other components and stressing orcracking them. The tongue and groove feature avoids this problem withoutrequiring the selection or designing of larger or longer headers. Thus,this arrangement avoids the problems associated with larger size headerssuch as higher cost, weight or decreased sensitivity.

A further advantage provided by the tongue and groove joiningarrangement of the present invention is that the additional weld areaprovided by the tongue and groove may also add to the strength of theport by increasing the effective wall thickness. The stress on the portcylindrical wall is determined by the inside and outside diameters ofthe weld thickness, the difference of which is indicated as T₁ in FIG.8, as well as by the pressures applied to the wall. However, to achievea thicker wall in this conventional arrangement, a greater weldpenetration may be required, causing potential heat stress to theinternal components, as described above.

The tongue and groove joining arrangement of the present inventionallows a thicker wall to be formed, without requiring such deeper weldpenetration and consequential thermal effects. As can be seen in FIG. 9,the total wall thickness T₂ in this case is determined by the radialthickness of the weld penetration plus the radial thickness of thetongue element 110. In this manner, a thicker wall may be formed,without requiring higher heat to weld the complete depth of the wall. Anequivalently thicker wall, and a stronger port, is achieved, withoutintroducing damaging thermal effects to the internal cavity.

Thus, the present invention provides an improved method of joining thepressure header to an associated body section, such as a port. Thisarrangement allows the measurement of very high external pressureswithout encountering joint or component failures, while also eliminatingthe problem of header components being damaged by a deep welding processduring fabrication. Additionally, the overall transducer unit isstrengthened by the increased wall thickness permitted by the tongue andgroove feature.

In yet another exemplary embodiment, and as illustrated in FIGS. 13 a-cand 14, the pressure transducer assembly of the present invention cancomprise a header 210 having a first connection portion 212, a port 215having a corresponding second connection portion 217, wherein the firstconnection portion 212 of the header 210 is attached to the secondconnection portion 217 of the port 215. An integral back up ring 205,used as a weld stop, may be defined in one of the header 210 and port215, and is separated from the header-port interface by a cavity 220.This configuration is slightly different than the tongue and groovejoining configuration described above, but it provides similar benefitsas it enables full penetration welds and prevents said weld fromdamaging/cracking a main body 225 of the header assembly 210.

Prior art embodiments have also utilized weld stops for high pressureheader welds, however many of the prior art embodiments poseshortcomings. For example, FIG. 10 illustrates a prior art transducerassembly that enables full penetration welds between the header-portinterface and provides a controlled stop at the rear of the weld, suchthat the root of the weld is turned 90 degrees from the weld plane, suchthat the leading ends, also known as “crack tips” (the crack tip iswhere the stress is highest, and is the initiating point for starting acrack), will be along the inner cylindrical surface of the header andport interface (such that the crack is propagated towards the outercylindrical surface), therefore placing the leading ends in compression,rather than tension. It was once believed that this configuration wouldlimit crack growth. Tests and further analysis, however, have shown thatthe root remains a concentrated pre-crack, and thus contributes tocracking and fatigue failures, regardless of root orientation.

In another prior art embodiment, and as illustrated in FIG. 11, abacking plate is used as a weld stop. As illustrated, the backing plateis placed on the back end of the plate-plate weld, and thus preventsweld splatter and/or prevents the flow of weld material out of the backof the weld. The backing plate of this embodiment, aids a welder thatcannot access both sides of the weld.

An alternative embodiment that enables cylindrical welding isillustrated in FIGS. 12-b. This embodiment was derived from theembodiment illustrated in FIG. 11, however the flat backing plateillustrated in FIG. 11 is replaced with a circular ring. The circularring is disposed on the inside of the header/port weld, which allows fora full penetration weld. In this embodiment, however, the weld does notcomprise the sharp root of the weld stop design illustrated in FIG. 10.This embodiment can be designed such that the overall stress applied tothe header is low enough to limit fatigue. Further, because there is nosharp weld root, the survival of the header is based on fatigue, ratherthan crack propagation, which improves survival rate as the number ofcycles before fatigue is reached is in the order of millions, whereascrack growth is in the order of thousands.

Exemplary embodiments of the present invention provide an alternativepressure transducer assembly that comprises a built-in weld stop. Aspreviously described, the pressure transducer assembly of the presentinvention comprises a header 210 having a first connection portion 212and a port 215 having a corresponding second connection portion 217. Thefirst connection portion 212 of the header assembly 210 is attached tothe second connection portion 217 of the port assembly 215, thuscreating a header-port interface. An integral back up ring 205, used asa weld stop, may be defined in one of the header 210 and port 215, andis separated from the header-port interface by a cavity 220. The cavity220 defines an empty space and does not contain additional components.

The main body 225 of the header 210 comprises a sensing elementpreferably adapted to measure an applied pressure. It shall beunderstood, however, that the sensing element may be adapted to measureother physical characteristics, such as temperature. The main body 225of the header 210 further comprises additional components that are inelectrical communication with the sensing element and are adapted tooutput a signal indicative of the sensed condition from the sensingelement. It is therefore important that the main body 225 of the header210 adequately encloses the sensing element and all other associatedelectrical components to protect said elements from externalenvironments. The port 215 attaches to the header and is adapted toshield the header 210 from external environments and provide an outershell that is compatible for fitting within the device being measured,such as a gas turbine engine.

In exemplary embodiments, the header 210 is secured to the port 215 viaa full penetration weld. Specifically, the first connection portion 212of the header 210 may be attached to the corresponding second connectionportion 217 of the port 215 via a full penetration weld that extendsradially inward towards the cavity 220. In prior art embodiments and asdescribed above, the full penetration weld between the header 210 andthe port 215 may penetrate beyond the header-port interface, whichcauses crack propagation within the header. This damages the header andinterferes with the header's ability to adequately shield the sensingelement and associated components, which consequently reduces thelifespan of the transducer assembly. The pressure transducer assembly ofthe present invention addresses this deficiency as the cavity 220 andthe integral back up ring 205 shields the main body 225 of the header210 from the full penetration weld and thus substantially minimizes oreliminates header crack propagation.

In one exemplary embodiment, the integral back up ring 205 can bedefined within the port, as illustrated in FIGS. 13 a-c. The integralback up ring 205 is opposite the second connection portion 217 of theport 215 and is separated from the second connection portion 217 of theport 215 via the cavity 220. Specifically, the integral back up ring 205extends along an axis and the second connection portion 217 extendsalong the same axis, and thus the elements are coaxial. The cavity 220is defined between the integral back up ring 205 and the secondconnection portion 217 such that at least a portion of the integral backup ring 205 and the second connection portion 217 are spaced apart. Theintegral back up ring 205 extends further along the axis than the secondconnection portion 217 of the port 215, such that when the firstconnection portion 212 of the header 210 and the second connectionportion 217 of the port 215 are welded together, the integral back upring 205 sufficiently blocks the main body 225 of the header from theweld.

In another exemplary embodiment, the integral back up ring 205 can bedefined within the header 210, as illustrated in FIG. 14. The integralback up ring 205 is opposite the first connection portion 212 of theheader 210 and is separated from the first connection portion 212 of theheader 210 via the cavity 220. Specifically, the integral back up ring205 extends along an axis and the first connection portion 212 extendsalong the same second axis, and thus the elements are coaxial. Thecavity 220 is defined between the integral back up ring 205 and thefirst connection portion 212 such that at least a portion of theintegral back up ring 205 and the first connection portion 212 arespaced apart. The integral back up ring 205 in this embodiment extendsfurther along the axis than the first connection portion 212 of theheader 210, such that when the first connection portion 212 of theheader 210 and the second connection portion 217 of the port 215 arewelded together, the integral back up ring 205 sufficiently blocks themain body 225 of the header 210 from the weld.

The full penetration weld that connects the first connection portion 212of the header 210 to the second connection portion 217 of the port 215extends radially inward towards the cavity 220. The cavity 220 providesa buffer between the weld and the integral back up ring 205, and theintegral back up ring 205 provides an additional buffer between the weldand the main body 225 of the header 210. Thus, if the weld extends pastthe header-port interface, the weld and associated stresses therein willeither be stopped or reduced by the cavity 220 and/or the integral backup ring 205 before it reaches the main body 225 of the header 210. Theshielding of the main body 220 of the header 210 from the fullpenetration weld, and the associated stresses therein, substantiallyminimizes and/or eliminates crack propagation within the header.

Further, because the integral back up ring 205 can be defined within theport 215 or the header 210, it eliminates the additional step ofpositioning a separate weld stop, as is the case for many of the priorart embodiments. It shall be understood that the specific dimensions ofthe port 215 and the header 210 may vary, as the pressure transducerassembly can be tailored to specific pressures and applications. FIGS.17 a-b provide dimensions for two exemplary embodiments of the presentinvention, however embodiments of the present invention are not limitedto the illustrated dimensions.

The foregoing description of the embodiments of this invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the embodiments of the inventionto the form disclosed, and, obviously, many modifications and variationsare possible. Such modifications and variations that may be apparent toa person skilled in the art are intended to be included within the scopeof this invention as defined by the accompanying claims.

1. A pressure transducer assembly, comprising: a header having a firstconnection portion; a port having a corresponding second connectionportion, wherein the first connection portion of the header is attachedto the second connection portion of the port to create a header-portinterface; and an integral back up ring defined in one of the header andport, wherein the integral back up ring is separated from theheader-port interface by a cavity.
 2. The pressure transducer assemblyof claim 1, wherein the first connection portion of the header isattached to the second connection portion of the port by a fullpenetration weld.
 3. The pressure transducer assembly of claim 2,wherein the full penetration weld extends radially inward towards thecavity.
 4. The pressure transducer assembly of claim 2, wherein theintegral back up ring is adapted to block the full penetration weld fromdamaging the header and minimize crack propagation.
 5. The pressuretransducer assembly of claim 4, wherein crack propagation is eliminated.6. The pressure transducer assembly of claim 1, wherein the firstconnection portion of the header and the second connection portion ofthe port have mating circular cross-sections.
 7. The pressure transducerassembly of claim 1, wherein the header comprises a sensing element. 8.The pressure transducer assembly of claim 7, wherein the sensing elementis a pressure sensor.
 9. A method of manufacturing a pressure transducerassembly, comprising: defining an integral back up ring in a header,wherein the header has a first connection portion; attaching the firstconnection portion of the header to a corresponding second connectionportion of a port thereby creating a header-port interface; and whereinthe integral back up ring is separated from the header-port interface bya cavity.
 10. The method of claim 9, further comprising welding thefirst connection portion of the header to the second connection portionof the port.
 11. The method of claim 9, wherein the integral back upring is adapted to block full penetration welds from damaging the headerand minimize crack propagation.
 12. The method of claim 9, wherein theheader comprises a sensing element.
 13. The method of claim 12, whereinthe sensing element is a pressure sensor.
 14. The method of claim 9,wherein the first connection portion, the second connection portion, andthe integral back up ring are coaxial.
 15. A method of manufacturing apressure transducer assembly, comprising: defining an integral back upring in a port, wherein the port has a first connection portion;attaching the first connection portion of the port to a correspondingsecond connection portion of a header thereby creating a header-portinterface; and wherein the integral back up ring is separated from theheader-port interface by a cavity.
 16. The method of claim 15, furthercomprising welding the first connection portion of the port to thesecond connection portion of the header.
 17. The method of claim 15,wherein the integral back up ring is adapted to block full penetrationwelds from damaging the header and minimize crack propagation.
 18. Themethod of claim 15, wherein the header assembly comprises a sensingelement.
 19. The method of claim 18, wherein the sensing element is apressure sensor.
 20. The method of claim 15, wherein the firstconnection portion, the second connection portion, and the integral backup ring are coaxial.